The overarching goal of Project 1 is to understand how the physicochemical composition and structure of engineered nanoparticles (ENPs) dictate their biological interaction with cells to ultimately affect signaling and physiology. We hypothesize that scavenger receptor pathways plays a prominent role in determining the intracellular dose of ENPs in macrophages and biodistribution of ENPs in vivo. We further hypothesize that ENPs that hijack' scavenger receptor uptake pathways may compromise macrophages ability to phagocytose and/or kill common bacterial lung pathogens. To test these hypotheses, microscopy, flow cytometry, and magnetic particle detection (MPD) will be used to quantitatively determine how varying the size, surface chemistry, charge and agglomeration state of ENPs (cerium oxides, silica oxides, iron oxides) affects their rate of uptake and trafficking pathways in macrophages derived from wildtype mice and mice deficient in class A scavenger receptors (Aim1). We will determine how the physicochemical properties of the ENPs affect stability of lysosomes, and their ability to activation inflammasome signaling (Aim 2). In vitro macrophage infection studies will be conducted to determine whether ENPs internalized by scavenger receptor pathways compromise the macrophages ability to recognize, phagocytosis and kill pathogens, using streptococcus pneumoniae as a model human lung pathogen (Aim 3). Finally, we will apply genomic microarray and bioinformatic analyses to identify gene regulatory pathways modulated by scavenger receptors and expore mechanisms by which ENPs may affect innate immune functions of macrophages (Aim 4). The dose-response studies in this project are designed to feed data directly for quantitative structure activity relationship analysis and development of dosimetry and risk models in Project 3. The results will also provide a molecular basis for experimental design and interpretation of parallel in vivo biodistribution and pathogen infection studies to be conducted in Project 2. We envision the proposed approach can provide quantitative data for hazard and risk analysis that is focused on clinically relevant measures of macrophage function that are potentially impacted by low level exposures to ENPs.